Of course, the most crucial factor was that these people never could have imagined someone logic-defying like Sheyan would appear here - someone who could finish Dons in the blink of an eye, not giving him any time to send a warning!
Moreover, their party was certainly not a silver party like Party Ace, so their communication range was much more limited. With the way the party had gone numb from waiting aimlessly, let alone 20 minutes, even if Sheyan took a 2-hour nap here, no one would probably notice.
Sheyan grew restless. He was eager to massacre all these people so that he could acquire the SARS disease. However, he knew he must remain cool-headed. He knew he must never underestimate the enemy under any circumstances.